A traditional method for the reduction of alkynes to trans-alkenes is to dissolve metal reduction using sodium or lithium in ammonia. However, we can also use Zinc as a metal to reduce alkynes.

In this specific case, by changing the proton source in the reaction, the dissolving Zinc metal reduction of ethyl phenylpropiolate to the corresponding cinnamate ester can be stereochemically controlled.

The product of the reaction will be a mixture of cis and trans ester. By this reaction, we can see the efficiency of Zinc in the reduction of alkynes.

The picture above shows a few of the steps in the creation of amphetamines. In these steps, tosyl chloride is added to (2,5-dimethoxyl-4-methylphenyl)-2-propanol to create the tosylate. After this step, the reaction can proceed in one of two ways. If the chirality of the amphetamine is not important, ammonia is added to the tosylate to give 2,5-dimethoxy-4-methylamphetamine. This reaction has an 80% yield, but has a racemic mixture of products because it is thought to be an SN1 reaction. If the chirality is important, the tosylate is converted into an azide with sodium azide, then hydrogenated using a paladium catalyst to form 2,5-dimethoxy-4-methylamphetamine. Forming the amphetamine using this method gives a final yield of about 77%. The chirality of the original alcohol is inverted by the tosylation, so reacting an (S)-alcohol with the tosyl-azide-hydrogen sequence would give an (R)-amphetamine, and vice versa.